1. Field of the Invention
The present invention relates to a vehicle-carried type fuel cell system provided with fuel cell stacks each comprising a plurality of fuel cell units each composed of a solid polymer ion exchange membrane interposed between an anode electrode and a cathode electrode, the plurality of fuel cell units being stacked in the horizontal direction with separators intervening therebetween.
2. Description of the Related Art
For example, the solid polymer type fuel cell comprises a fuel cell unit including an anode electrode and a cathode electrode disposed opposingly on both sides of an ion exchange membrane composed of a polymer ion exchange membrane (cation exchange membrane) respectively, the fuel cell unit being interposed between separators. Usually, the solid polymer type fuel cell is used as a fuel cell stack comprising a predetermined number of the fuel cell units and a predetermined number of the separators which are stacked with each other.
In such a fuel cell stack, a fuel gas such as a hydrogen-containing gas, which is supplied to the anode electrode, is converted into hydrogen ion on the catalyst electrode, and the ion is moved toward the cathode electrode via the ion exchange membrane which is appropriately humidified. The electron, which is generated during this process, is extracted for an external circuit, and the electron is utilized as DC electric energy. An oxygen-containing gas such as a gas containing oxygen or air is supplied to the cathode electrode. Therefore, the hydrogen ion, the electron, and the oxygen gas are reacted with each other on the cathode electrode, and thus water is produced.
When the fuel cell stack as described above is carried and used on a vehicle or the like, it is necessary to provide a considerably large number of fuel cell units in order to obtain desired electric power. In such a situation, when it is intended to construct a single fuel cell stack by stacking a considerable number of fuel cell units, the length of the fuel cell units is considerably long in the stacking direction. As a result, for example, an inconvenience arises such that the fuel gas cannot be supplied uniformly to the respective fuel cell units. In view of the above, a fuel cell system is adopted, which is constructed such that a plurality of fuel cell stacks are arranged in parallel to one another, and the fuel cell stacks are electrically connected in series to one another.
In the case of such a fuel cell system, various artifices are made in order to simplify the connection structure when the fuel cell stacks, which are arranged in parallel to one another, are electrically connected in series. For example, in Japanese Laid-Open Patent Publication No. 8-171926, fuel cell stacks, which are arranged in parallel to one another, are allowed to have different electric polarities at respective stacking ends. A terminal plate, which is formed with an engaging projection, is provided at one of the stacking ends. A terminal plate, which is formed with an engaging recess capable of engaging the engaging projection, is installed at the other stacking end.
Accordingly, the fuel cell stacks, which are arranged in parallel to one another, can be electrically connected in series to one another only by engaging the engaging projection and the engaging recess of the respective terminal plates with each other. Further, the fuel cell stacks are mutually slidable in the stacking direction in an amount corresponding to the thickness of the terminal plate.
However, in the case of the conventional technique described above, the fuel cell stacks are slidable in the stacking direction in the amount corresponding to the thickness of the terminal plate, owing to the engagement between the engaging projection which is provided for one of the terminal plates and the engaging recess which is provided for the other terminal plate. Therefore, it is difficult to allow the fuel cell system to be carried especially on the vehicle or the like.
That is, when the fuel cell system is carried on the vehicle or the like, any shaking movement tends to occur on the fuel cell system in a variety of directions, for example, due to vibration during running, variation in rate of acceleration, and repetition of start and stop. For this reason, the following problem is pointed out. That is, any relative positional discrepancy consequently arises in the fuel cell stacks which are arranged in parallel to one another. Any stress acts on the terminal plate which is installed at the stacking end of each of the fuel cell stacks.